Fluid coking process incorporating gasification of product ore

ABSTRACT

A heavy carbonaceous material such as petroleum residuum (1,050* F.+) is converted completely to distillate and gaseous products by an integrated process consisting of a conventional fluid coking reactor, a circulating coke heater, and a gasifier in which the coke formed in the reactor is converted to an H2 and CO rich gas by reaction with steam and an oxygen-containing gas. The process can also be operated by yield a net product of good quality coke.

United States Patent 3,66 1 ,543

Saxton 1 May 9, 1972 154] FLUID COKING PROCESS 3.542.532 11/1970 Johnsonet a1 .208/127 8 et X 2,600,430 6/1952 Rlbletl ..48/206 x PRODUCT ORE2,605,215 7/1952 Coghlan ..201/1 6 x Inventor: Arthur L. Saxton, WarrenTownship, NJ.

Assignee: Esso Research and Engineering Company Filed: Nov. 26, 1969Appl. No.: 880,219

US. CL; ..48/206, 48/63, 23/204 M, 23/212 R, 201/31, 201/44, 208/127Int. Cl ..Cl0j 3/00,C10b 49/10 FieldoiSearch... ..20l/15,16,14,13,17,31,201/44; 48/206, 63; 208/127; 23/204 M, 212 R References Cited UNITEDSTATES PATENTS 2/1955 Keith ..208/127 GAS FRA T GAS 011.

STEAM Primary Examiner-Norman Yudkoff Assistant Examiner-David EdwardsAttorney-Pearlman and Stahl and C. D. Stores [5 7] ABSTRACT A heavycarbonaceous material such as petroleum residuum 1,050" F.+) isconverted completely to distillate and gaseous products by an integratedprocess consisting of a conventional fluid coking reactor, a circulatingcoke heater, and a gasifier in which the coke formed in the reactor isconverted to an H and CO rich gas by reaction with steam and anoxygen-containing gas. The process can also be operated by yield a netproduct of good quality coke.

10 Claims, 1 Drawing Figure 1101' COKE ASH P'ATENTEDHM 9 1972 moSmEGE5200 w $5 INVENTOR.

ATTORNEY mdbxz kudxmu mun -mum FLUID COKING PROCESS INCORPORATINGGASIFICATION OF PRODUCT ORE BACKGROUND OF THE INVENTION In conventionalfluid coking, the carbonaceous feed is injected into a bed of fluid cokewhere it is cracked to vapors and coke. The vapors pass through acyclone to a scrubber/fractionator where they are fractionated to gas,naphtha and oil products, and a heavy stream which is recycled to thecoking reactor. A circulating stream of coke is stripped in the bottomzone of the reactor and transferred to a coke burner where sufficientair is injected for burning part of the coke and heating the remaindersufficiently to satisfy the heat requirements of the coking reactor whenthe unburned hot coke is recycled thereto. Net coke above that consumedin the burner is withdrawn as product coke.

Unfortunately, the market for this coke has been limited with the resultthat attempts have been made to increase its value by subsequenttreatment such as high temperature calcining and briquetting.Alternatively, the coke can be converted to an H and CO rich gas in asubsequent processing step by reaction with steam and anoxygen-containing gas. None of these subsequent coke processing stepshas been found to be economically attractive for general use.

Furthermore, when processing typical petroleum residuum in aconventional fluid coker, the combustion products from the burner havean undesirably high SO content which is an atmospheric pollutant.

The two above problems low market value of the product coke, andatmospheric pollution from the burner have limited the use of fluidcoking which is otherwise a superior residuum conversion process.

SUMMARY OF THE INVENTION ficulties can be overcome and theattractiveness of the basic fluid coking process greatly enhanced byreplacing the coke burner used in the normal fluid coking process withan integrated coke heater and gasifier system comprising two fluidizedbeds of coke separated by a grid or other means, wherein coke isgasified in the lower'zone in'the presence of steam and air orcommercially pure oxygen forming hotgases which pass into the upper bed,releasing heat which is transferred to the reactor via a circulatingcoke stream.'-Altematively, the gases from the gasification zonecould'be combined with the circulating coke'from the reactor andconducted through a transfer line into a separator vessel'from which thehot coke circulates back to the reactor to supply its heat requirements.In either case, entrained coke will also pass to the heater'to provideadditional heat for the coker-reactor. Air, or other oxygen-containinggas may be added to the heating zone to burn a portion of the CO andhydrogenand thus provide any additional heat which is required tosatisfy the coking reactor heat requirement.

The gas product from the heater is rich in H, and CO and is anattractive feed gas for manufacturing a concentrated H stream via thewell-known'water-gas-shift reaction, or' for BRIEF REFERENCE TO THEDRAWING The invention will be better understood by reference to theaccompanying drawing which shows in diagrammatic form suitable apparatusfor carrying out a preferred embodiment of the invention.

PREFERRED EMBODIMENT OF THE INVENTION Referring now to the drawing, acarbonaceous material having a Conradson carbon of about 15 percent,such as heavy residuum boiling l,050 F.+, or a coal charslurry, ispassed into coking zone 1 by line 2, manifold 3 and multiple feednozzles represented by lines 4, 5, 6, 7 and 8 onto a fluidized bed ofsolids, e.g., coke of 40 to 1,000 microns in size, having an upper levelL. A fluidizing gas,e.g., steam, is admitted to the base of the vesselthrough line 9 in amounts sufficient to obtain superficial fluidizinggas velocities in the range of 0.5 to 4 ft./sec. Coke at a temperatureto 300 F. above the coking temperature is admitted to the coker-by line10 in amounts sufiicient to maintain a coking temperature in the rangeof 900 to l,200 F. The lower portion of the coker serves as a strippingzone to remove occluded hydrocarbons from the coke. Coke is withdrawnfrom this stripping zone by line 11 and is circulated to heater l2.Conversion productsare passed through cyclone l3 to remove entrainedsolids which are returned to the coker through dipleg 14. The vaporsleave the cyclone through line 15 and pass into scrubber-fractionator 16where they are fractionated to gas leaving by line 17 naphtha by line 18and gas oil by line 19. A heavy stream is removed through line 20, aportion of which is circulated through conventional heat removalexchangers and returned to scrubber as pumparound by line 21; anotherportion is recycled to the coker by line 22. The small amount of finesolid particles which pass through the reactor cyclone is returned tothe coker reactor with this recycle stream.

In heater 12, stripped coke from the reactor (commonly called cold coke)is introduced by line 1 1 to a fluid bed of hot coke having .a level L.The bed is heated by fuel gas passing upward through disc and donutdistributor 23 and egg crate baffle 24. Hot coke is removed from thefluidized bed in heater 12 by line 25 and a portion is passed by line 26to a bed of fluidized coke having a level L in gasifier 27. Anotherportion is recycled to the coker by line 10 to supply heat thereto. Thecoke introduced to'the fluidized bed in the gasifier 27 is contactedwith steam introduced by line28and air or oxygen by line 29 where thefollowing reactions take place:

When coke is oxidized,the initial product is a mixture of CO and CO asshown inequation "1. At temperatures of 1,600" F.+ in the presence ofoxygen, C0 is rapidly oxidized to CO according to equation 2. Afteroxygen has been exhausted, CO reacts with carbon to form CO. At hightemperatures, equilibrium favors drawingequation' 3-to the rightto formCO. Low pressure also favors this'reaction. Reaction 3 isslower'thanreaction 2. Thus,equilibrium would favor very reaction isslightly endothermic and when steam issubstituted for some of theoxygen, the, gasification zone temperature drops at a constant quantityof coke gasified. Finally, water reacts with C0 to produce CO andhydrogen inthe water gas shift represented by equation 5. Most of thesulfur in the coke will be converted to H S with a very small amount ofCOS being formed.

The gases formed by the above reactions pass upwardly through thegasifier and into, the heater by way of the narrow neck portion 30.Additional air or oxygen may, be admitted to the heater by lines 31 toburn a small portionof these gases .and supply additional heat to thecoke in the heater. The gases Mol.% Including Mol.% Excluding ,0 i-i11,0 as H, 6.5 as 11.0 2.9 co 19.9 20.6 co, 1.9 8.2 N, 61.9 64.4 ms 0.9i

Net heating value on a dry basis is 84.6 BTU/SCF. When oxygen is usedfor gasification, a typical composition of the gas Net heating value ondry basis is 224 BTU/SCF. Small quantities of cracked hydrocarbonmaterials will also be present in the product gases and will increasethe heating value of the product gases. The quantity and compositionwill vary somewhat depending on the coker reactor feed and on reactionand stripping conditions.

Some net product coke may be withdrawn if desired through line 33.Agglomerates of foreign solids, which mayform in some cases, can also bepurged via this line through an elutriator from which any included cokecan be blown back into the gasifier.

While the process has been described with respect to the circulation ofcoke as the fluidized medium used in the process, it is to be understoodthat a captive bed of fluidized inert particles, such as alundum ormullite, may be used in the gasifier 27. This can. be advantageous forsystems in which substantial quantities of very fine about p.) particlesof foreign solids are released inthe gasifier such that very lowvelocities would be required in order to maintain a stable fluidizedbed. Such a captive bed can be fluidized readily without significantentrainment of the captive bed particles at superficial velocitiessubstantially higher than the entrainment velocity of line particlesreleased from the coke. Such a captive bed provides a well mixedreaction zone in the gasifier in which the carbon can be burned and theforeign solids released without causing severe fluidization problems.Some equilibrium concentration of the fine particles are retained in thegasifier bed, thus providing-sulficientresidence time for completegasification of the carbon before the bulk of the particles areentrained by the exit gases. The hot gasifier products, includingentrained solid particles, pass through a heat exchangebed similar tothe bed described in connection with heater 12. In this heat exchangebed the coke from the reactor would be heated as required to satisfy thereactor heat balance. This type of process would be preferable whenprocessing feeds containing much higher solids than are normally presentin petroleum residuum, e.g., bitumen from coal, tar sands or shale whichmay contain -20 percent inert solids. The solids, such as fine sand,metal oxides, or the like, contained in the bitumen are released in thecaptive bed in the gasifier and being smaller than the coke are moreeasily entrained out and carried upwardly through the heat exchange bed.These fine particles will also pass through the conventional cyclones inthe heater vessel but can be recovered by a downstream electricalprecipitator.

EXAMPLE A Kuwait vacuum residuum containing 5.5 wt. percent suifur,boiling l,050 F.+ and having a Conradson carbon of 21.8 is introducedinto the fluidized bed of coker 1, operating at 975 F. The coke producedis passed to heater 12 at 950-975 F. and heated with gases from gasifier27 at 1,800 F. This gas is formed from coke gasified in gasifier 27 byair or oxygen and steam introduced thereinto. The gas leaves the heaterat 1,150 F. After transferring heat to the circulating coke. Virtuallyall solid material is removed from the gas by cyclone 32.

Steam/air rates are controlled to maintain the gasifier bed at atemperature of about 1,800" F. The heater operates at a pressure of 20psig and the gasifier at 25 psig.

The following data are obtained:

TABLE 1 Operating Conditions and Feed and Product Compositions CokerFeed and Operating Conditions Coker feed Rate 12,000 B/SD Source Kuwait1050F.+Residuum Con. carbon, wt.% 21.8 Sulfur, wt.% 5.5 Gravity, APl 5.7Va, ppm 1 13- Ni, ppm 25 Totalash, ppm 252 Operating conditions Reactortemperature, F. 975 Reactor product final cut point, F. 950 Cokecirculation rate, tons/min. 15.5 Heater zone temperature, F. l 150pressure, psig 20 Gasifier zone temperature, F. 1800 pressure, psig 25Coke composition Gross Oil Net to gasification Hydrogen, wt.% 6.0 14.7Carbon, wt.% 86.6 77.9 90.1 Sulfur, wt.% 7.4 7.4 7.4 Va, ppm 410. Ni,ppm Total ash, ppm 906 Air/Steam Oxygen/Steam Product gas compositionGasification Gasification Composition, mol.%

CO 20.4 42.0 CO, 6.6 18.0 H, 4.4 18.7 11 0 1.4 6.7 (C1-1) 5.0 1 1.01-1,S 1.2 2.6 N, 61.0 1.0

100.0 100.0 Fuel gas heating valve (Hi-1V) BTU/SCF (ex. H,S) 150 350 Thematerial balance on the heater gasifier is as follows:

TABLE IL-HEATER-GASIFIER HEAT AND MATERIAL BALANCE Material Balance!(Number for oxygen/steam gasificatlon shown in parenthesis wheredifferent from air/steam gaslfication.)

Cold coke Hot coke Air or from Entrained to Steam (oxygen) Steam reactoroil reactor Temp F. 350 353 975 075 l, 150 M#/hr 4(14) 1, S 14. 4 1, 8606, 030(1,070) ACF/miu Supplemcntary Gasifier Euair (or stage trainedoxygen) Gasifier product coke to to upper Product feed gas heater zonegas 'Iemp., F 1,150 1,800 1,800 360 1,150 Mi /hm--- 136(132) (96)=Mol/hr 8,100(3, 917) 1, 630(460) 9, 980(4, 445) MACF/min- 82. 3(39. 9)83. 7(37. 4)

Heater section heat balance Air/steam Oxygen/steam Heat load:

Heat to circulating coke 130. 0 130. 0 Entrained oil heat of cracking 6.0 5. 0 Heat to transfer line steam 3. 4 3. 4 Heater heat losses 3. 6 3.6

Total 142. 0 142.0

Heat supply:

Gas from gasifier 42. 0 20. 1 Entrained coke 28. 6 28.6 Combustion of C0and H2111 heater.. 7]. 4 93. 4

Total 142. 0 142. 0

It will be appreciated that operating conditions, product gascomposition and the overall heat and material can vary substantiallyfrom the above data, depending on such variables as the coker reactorfeed and the coker product objectives.

The nature and advantages of the present invention having been fully setforth and examples of the same given, what is claimed as new, useful,and unobvious and desired to be secured by Letters Patent is:

1. An integrated fluid coking-gasification process which comprises:

treating a carbonaceous material in a low pressure fluid coking zonecomprising a fluid bed of particles operating at a temperature betweenabout 900 and about l,200 F. to produce coke and light hydrocarbonmaterial, some of which may adhere to said coke; i a a? heating to ahigher temperature said coke in a low pressure heating zone comprising aseparate fluid bed of particles;

passing a portion of said heated coke to said fluid coking zone andanother portion of said heated coke to a low pressure gasification zone;

contacting said heated coke in said gasifying zone with steam and anoxygen-containing gas to produce a metalrich ash and a gaseous streamcontaining hydrogen and carbon oxide gases;

passing said ash and gaseous stream to said heating zone to provide asubstantial part of the heat required in said heating zone;

recovering said gaseous stream of said heating zone.

2. A process according to claim 1 wherein the pressure in said fluidcoking zone, said heating zone and said gasifying zone is less thanabout 3.0 atmospheres.

3. A process according to claim 1 wherein said gasifying zone comprisesa separate bed of fluidized particles.

4. A process according to claim 3 wherein said gaseous stream leavingsaid gasifying zone passes through a distributing zone before enteringsaid heating zone to provide for more even gas flow in said heatingzone, as well as, better fluidizing of said heating zone bed.

5. A process according to claim 4 wherein additional oxygen-containinggases are mixed with said gaseous stream and said mixture passed throughsaid distributing zone and then into said heating zone.

6. A process according to claim 1 wherein said coke produced in saidfluid coking zone is passed through a stripping zone and contacted witha stripping gas to remove a major portion of said adhering lighthydrocarbon material before said coke is heated in said heating zone.

7. A process according to claim 6 wherein said stripping gas is steam.

8. A process according to claim 1 wherein said metal-rich ash isrecovered from said heating zone by cyclone means.

9. A process according to claim 5 wherein a portion of said metal-richash is recovered from said gasifying zone.

10. A process according to claim 1 wherein a portion of said steamtreated, heated coke in said gasifying zone is removed from saidgasifying zone.

2. A process according to claim 1 wherein the pressure in said fluidcoking zone, said heating zone and said gasifying zone is less thanabout 3.0 atmospheres.
 3. A process according to claim 1 wherein saidgasifying zone comprises a separate bed of fluidized particles.
 4. Aprocess according to claim 3 wherein said gaseous stream leaving saidgasifying zone passes through a distributing zone before entering saidheating zone to provide for more even gas flow in said heating zone, aswell as, better fluidizing of said heating zone bed.
 5. A processaccording to claim 4 wherein additional oxygen-containing gases aremixed with said gaseous stream and said mixture passed through saiddistributing zone and then into said heating zone.
 6. A processaccording to claim 1 wherein said coke produced in said fluid cokingzone is passed through a stripping zone and contacted with a strippinggas to remove a major portion of said adhering light hydrocarbonmaterial before said coke is heated in said heating zone.
 7. A processaccording to claim 6 wherein said stripping gas is steam.
 8. A processaccording to claim 1 wherein said metal-rich ash is recovered from saidheating zone by cyclone means.
 9. A process according to claim 5 whereina portion of said metal-rich ash is recovered from said gasifying zone.10. A process according to claim 1 wherein a portion of said steamtreated, heated coke in said gasifying zone is removed from saidgasifying zone.